秦岭林区径流水化学对雨水酸化的响应

在秦岭南坡天然林分布地带选择火地塘典型林区,测定区内雨季降雨和流域出口径流水样pH值及水化学成分,探讨秦岭林区径流水化学对雨水酸化的响应.结果表明:长期雨水酸化可导致林区径流pH值降低,Ca2+和Mg2+浓度降低,K+和Na+浓度变化与雨水酸化关系不大;径流Zn,Pb和Cd浓度对雨水酸化响应不明显,酸化雨水未导致森林土壤富集的重金属释放.     

Long-term influence of stream water chemistry in Japanese cedar plantation after clear-cutting using the forest rotation in central Japan

Because both natural and anthropogenic disturbances affect biogeochemical cycles in forest ecosystems, monitoring is needed to separate their influences. Chronosequence is very useful for such studies. In our study area, plantation through forest rotation on a watershed basis resulted in more than 40 adjacent watersheds of between 0 and 87 years of stand age, kind of chronosequence. Here, we examined the biological similarity of the watersheds and the long-term effects of clear-cutting on stream water chemistry. The stream water NO₃⁻–stand age relationship was similar between the two observation years; stream water NO₃⁻ concentrations increased dramatically in the watersheds after clear-cutting and decreased in 7–10-year-old replanted watersheds. The slope of stream water NO₃⁻ concentrations between the different watersheds covered by same age stand was significant, at 1:1. Additionally, stream water NO₃⁻ concentrations were more strongly correlated between the different watersheds covered by same aged stand than between the observations at 4 years intervals within a watershed. These findings indicate that stream water NO₃⁻ concentration is mainly regulated by stand age, i.e., by vegetation regrowth, rather than watershed-specific characteristics. Hence, adjacent watersheds are biologically similar apart from stand age and can be regarded as a chronosequence. While there was a clear relationship between stream water NO₃⁻ concentration and stand age, there was significant correlation with stream water SO₄²⁻, Ca²⁺, Mg²⁺, Cl⁻ or Na⁺ between two observations in the same watershed. This indicates that watershed-specific characteristics, rather than vegetation regrowth, control stream SO₄²⁻, Ca²⁺, Mg²⁺, Cl⁻, and Na⁺ concentrations. After 25 years of clear-cutting Ca²⁺, Mg²⁺ and Na⁺ concentrations significantly increased. It is likely the contribution of forest floor accumulation with stand development. Based on these results, clear-cutting influences stream chemistry, not only NO₃⁻, but also the major cation and the influence of clear-cutting continues for several decades at this study site.     

南水北调中线水源林水质年际变化及趋势——以秦岭火地塘天然林为例

在南水北调中线水源地天然林分布区--秦岭南坡中山地带,选择火地塘林区2个小流域及2个支沟集水区,对8年间径流水化学成分年际变化及其影响因素进行分析.结果表明:火地塘林区径流pH值年际变化总体上呈降低趋势,NO-3、NH 4、Ca、Mg及Cd 浓度呈上升趋势,主要与当地汽车尾气排放等交通污染有关;Pb浓度上升为土壤吸附Pb解吸或含Pb矿物的溶解所致;K、PO3-4、Na、Mn及Zn浓度呈降低趋势缘于森林植被的逐渐恢复. 据此对南水北调中线水源地天然林水质发展趋势进行初步预测,结果表明:中线水源地天然林径流pH值将呈降低趋势,NO-3、NH 4、Ca及Mg浓度会上升,但均不会对水质造成较大的不利影响;K、PO3-4、Na、Mn、Zn浓度亦将呈降低趋势,其中PO3-4浓度降低有利于缓解丹江口水库水质富营养化的威胁;Cd、Pb浓度可能上升,应引起重视.     

A meta-analysis of the effects of nitrogen additions on base cations: Implications for plants, soils, and streams

The dominant base cations (BC; i.e., Ca²⁺, Mg²⁺, K⁺, and Na⁺) are important in buffering soil and water acidity in both terrestrial and aquatic ecosystems. Ca²⁺, Mg²⁺, and K⁺ are also important in many plant physiological functions. Because BC availability is affected by changes in the nitrogen (N) cycle, we conducted a meta-analysis of previously published data to determine if N fertilization alters the availability of BC in terrestrial and stream ecosystems across biomes. We include data from 107 independent studies published in 62 different articles, taking a holistic perspective on BC by examining their responses to added N in plant foliage, bulk soil, soil solution, and stream water. Our results suggest N fertilization may accelerate BC loss from terrestrial ecosystems over time periods less than five years. We found that N additions resulted in an overall 24% decrease in the availability of exchangeable Ca²⁺, Mg²⁺, and K⁺ in the bulk soil of boreal forest, temperate forest, and grassland biomes. Collectively, responses of BC in boreal forest, temperate forest, tropical forest, and grassland biomes increased following N fertilization by about 71% in soil solution and 48% in stream waters. Additionally, BC responses in foliage decreased in boreal forest and temperate forest biomes following N additions over time periods less than five years, but there were no significant changes over longer time periods. Despite large short-term shifts in BC responses following N additions, we did not find evidence of widespread negative impacts on ecosystems over time periods greater than five years. This analysis suggests effects of N addition on the availability of exchangeable BC may diminish over time. Although the effects on BC can be substantial over periods less than five years, there is little available evidence that N fertilization has had large-scale detrimental effects on the availability of BC needed for plant growth within terrestrial or aquatic ecosystems.     

An assessment of rainfall modification in mountainous ecosystems dominated by Fagus sylvatica L. and Picea abies (L.) Karst. (Western Balkans,Bulgaria) by multivariate analyses

Bulk precipitation, throughfall, and stemflow samples were collected in Petrohan site (Western Balkan, Bulgaria), operating in the framework of the Long-Term Ecological Research network, during a 6-year period (1995–2000). This mountain area is characterized by the presence of beech and spruce forests (Fagus sylvatica L. and Picea abies (L.) Karst.) and is utilized for drinking water supply. All samples were analyzed for pH and major inorganic anions (Cl^?, NO₃ ^?, and SO₄ ^2?) and cations (Ca²⁺, K⁺, Mg²⁺, Na⁺, and NH₄ ⁺). Results show that bulk precipitation in this region is mainly acidic (pH = 5.1), and the dominant neutralization components in the rainwater are Ca²⁺ and NH₄ ⁺. As for Ca²⁺, K⁺, Mg²⁺, Cl^?, and SO₄ ^2?, they are not originated by marine source. Cluster analysis and principal component analysis were used for investigating the possible sources contributing to the chemical composition of the bulk precipitation and its possible modifications during the passing through beech and spruce stands. Results highlight that local and long-range transport-related anthropogenic sources and natural sources contribute to the anion and cation content of the bulk precipitation. The enrichment of the solution through the foliage made up of dry depositions is significant in both stands, but canopy leaching processes are much greater in the spruce forest, especially for Ca²⁺. As for the stemflow, it follows the same pattern as the throughfall, but N uptake and a strong K⁺ and Mg²⁺ leaching are observed mainly in the spruce stand.     

重庆酸雨区缙云山典型林分冠层酸雨淋洗特征

选取重庆缙云山的针阔混交林、常绿阔叶林、毛竹林、灌木林4种典型林分,观测酸性降水过程中林外雨、穿透雨及干流等林内水分转换分量中的主要离子含量变化,分析林分冠层对雨水化学组成的影响,结果表明:(1)降雨中的离子当量浓度大小依次是SO42-＞Ca2+＞ NH4+＞Mg2+＞K+＞Na+＞NO3-;(2)降雨经过林冠层后pH值降低,干流的酸化程度增加最大;(3)降雨经林冠层后离子浓度明显增加(除灌木林),穿透雨中通量增加最大的阴离子和阳离子分别为SO42-(2.19×103～6.47×103 eq·hm-2)和Ca2+(1.41×103～3.39×103 eq-hm-2),离子来源主要为大气沉降和植物分泌物或淋出;(4)同一离子在不同林分的干流和穿透雨中的通量变化不同,反映出不同林分冠层的离子交换性差异.在针阔混交林中,林下降雨净淋溶量大小顺序为SO42-＞Ca2+＞ NO3-＞K+＞NH4+＞Mg2+＞ Na+;常绿阔叶林为SO42-＞ Ca2+＞ K+＞NO3-＞ NH4+＞ Mg2+ ＞Na+;毛竹林为Ca2+＞ SO42-＞ K+＞NO3-＞ NH4+＞Na+＞Mg2+;灌木林为Ca2+＞ NO3-＞ K+＞ Na+＞Mg2+＞ NH4+＞ SO42-.     

Shifting cultivation effects on creek water quality around Barkal Upazila in Chittagong Hill Tracts, Bangladesh

We report the effects of shifting cultivation on water quality in 16 creeks investigated once in 2007 and twice in 2008 in 16 apparently similar small neighboring watersheds,each of 3 to 5 ha,at four locations around Barkal sub-district under Rangamati District of Chittagong Hill Tracts in Bangladesh.Concentrations of SO 4 2and K +,and pH in creek water were lower,and NO 3-N and Na + concentrations were higher in shifting-cultivation land compared to land with either plantation or natural forest or a combination of these cover types.Shifting cultivation effects on some water quality parameters were not significant due to change in land cover of the watershed between two sampling periods either through introduction of planted tree species or naturally regenerated vegetation.Conductivity and concentrations of HCO 3,PO 4 3,Ca 2+ and Mg 2+ in creek water showed no definite trend between shifting cultivation and the other land cover types.At one area near the Forest Range Office of Barkal,creek water pH was 5.8 under land cover with a combination of shifting cultivation and plantation.At this area Na + concentration in shifting-cultivation land ranged from 32.33 to 33.00 mg L-1 and in vegetated area from 25.00 to 30.50 mg L-1 in 2007.At another area,Chaliatali Chara,SO 4 2concentration in a shifting-cultivation watershed ranged from 4.46 to 10.51 mg L-1,lower than in a vegetated watershed that ranged from 11.69 to 19.98 mg L-1 in 2007.SO 4 2concentration in this shifting-cultivation area ranged from 1.28 to 1.37 mg L-1 and in the vegetated area from 1.37 to 3.50 mg L-1 in 2008.     

Stream water and soil solution responses to 5 years of nitrogen and sulfur additions at the Fernow Experimental Forest,West Virginia

To examine the effects of elevated N and S inputs on a central hardwood forest, a whole-watershed acidification experiment was initiated in 1989 on the Fernow Experimental Forest, West Virginia. Annual experimental additions of 40 kg S ha⁻¹ year⁻¹ and 35 kg N ha⁻¹ year⁻¹ as ammonium sulfate fertilizer were applied to a 34 ha watershed with a 25-year-old stand of central Appalachian hardwoods. An adjacent watershed served as the control. After 5 years of treatment (total additions of 275 kg S ha⁻¹ and 220 kg N ha⁻¹), stream water NO₃⁻, Ca²⁺, Mg²⁺ concentrations and export increased. Soil solution concentrations provide evidence that the treatment watershed is nitrogen-saturated, which was unexpected for such a young stand. No statistically significant changes in annual SO₄²⁻ export were observed, but peak stream water concentrations of SO₄²⁻ did increase during the treatment period. Changes in soil solution chemistry suggest that the treated watershed also may be approaching SO₄²⁻ saturation.     

Deposition pattern of precipitation and throughfall in a subtropical evergreen forest in south-central China

The effects of dry deposition, canopy leaching, precipitation ion concentration, and precipitation H⁺ concentration on net throughfall flux (NTF, throughfall minus bulk precipitation) were evaluated on a seasonal basis by using a multiple regression analysis approach based on an observation period of 4 years in Shaoshan subtropical mixed evergreen forest, south-central China. Regression analysis results indicated that the estimated canopy exchange flux was the dominant factor regulating the NTF and the calculated dry deposition was a minor term. The seasonal dry deposition of base cations accounted for 15%–43% of the NTF. The NTF analysis showed that K⁺, Ca²⁺, Mg²⁺, Na⁺, and weak acids in throughfall were derived from foliar leaching and the canopy uptakes of H⁺, NH₄ ⁺, and NO₃ ⁻ were from precipitation. The retention rate of proton (H⁺ and NH₄ ⁺) in the canopy was close to the canopy leaching rate of base cations when corrected for weak acids because weak acid-induced canopy leaching did not exchange with protons, which suggested that the canopy leaching processes neutralized acid precipitation in Shaoshan forest.     

云南丽江拉市海汇水区不同森林枯落物的持水性能

对云南丽江拉市海汇水区面山上6种不同森林群落的枯落物储量和持水性能进行了测定,结果表明:不同森林群落的枯落物储量和持水性差别较大,其枯落物储量从最大的黄背栎林(22.45 t·hm-2)到最小的云南松林(6.54 t·hm-2),均是半分解与分解层的储量大于未分解层的储量;6种森林枯落物的最大持水量,除滇杨林外均是半分解与分解层的大于未分解层的,其最大总持水量排序为黄背栎林(60.77 t·hm-2)丽江云杉林(36.42 t·hm-2)云南松+黄背栎+杜鹃混交林(33.18 t·hm-2)川滇高山栎林(29.23 t·hm-2)滇杨林(18.82 t·hm-2)云南松林(13.72 t·hm-2)。各层枯落物的吸水速率均随浸水时间的延长而逐渐降低,在2 4 h后明显减缓,最终趋于零;且半分解与分解层的吸水速率均大于未分解层。6种森林枯落物的拦蓄水量也表现出半分解与分解层大于未分解层的规律,从大到小依次为黄背栎林(66.94 t·hm-2)丽江云杉林(41.24 t·hm-2)云南松+黄背栎+杜鹃混交林(36.80 t·hm-2)川滇高山栎林(32.99 t·hm-2)滇杨林(21.18 t·hm-2)云南松林(16.59 t·hm-2),降雨拦蓄量深分别为6.70、4.12、3.68、3.30、2.12、1.66 mm。     

Acid deposition effects on forest composition and growth on the Monongahela National Forest,West Virginia

The northern and central Appalachian forests are subject to high levels of atmospheric acid deposition (AD), which has been shown in some forests to negatively impact forest growth as well as predispose the forest system to damage from secondary stresses. The purpose of this study was to evaluate the possible contribution of AD to changes in composition and productivity of the Monongahela National Forest, and to evaluate soil-based indicators of acidification that might be useful for detecting AD-related forest changes. Soils adjacent to 30 Forest Inventory and Analysis (FIA) sites were sampled and analyzed for a suite of acidity indicators. These indicators were correlated with the periodic mean annual volume increment (PMAVI) of the forest stands on FIA plots for the 10-yr period 1989–2000. PMAVI ranged from −9.5 to 11.8 m³ ha⁻¹ yr⁻¹, with lower-than-expected growth (<3 m³ ha⁻¹ yr⁻¹) on two-thirds of the sites. In the surface horizon, effective base saturation, Ca²⁺ concentration, base saturation, K⁺ concentration, Ca/Al molar ratio, and Mg/Al molar ratio, were positively correlated with PMAVI and Fe concentration was negatively correlated with PMAVI (p ≤ 0.1). In the subsurface horizon pH_(w) and effective base saturation were positively correlated and Al³⁻ concentration and K⁺ concentration were negatively correlated with PMAVI. We hypothesized that NO₃-N/NH₄-N ratio would also be correlated with PMAVI, but it was not. Correlations between soil chemical indicators and PMAVI suggest that AD may contribute, in part, to the lower-than-expected forest growth on the Monongahela National Forest.     

广州市酸雨对不同森林冠层淋溶规律的研究

１９９８年４月至１９９９年３月对广州市白云山马尾松林和常绿阔叶林、广州市龙眼洞马尾松林两试验点进行了酸雨的监测,并测定和分析了林内穿透雨物理量及化学量,旨在探讨酸雨对不同森林冠层养分淋溶规律的影响。结果表明：（１）广州市酸雨占次数的７９．７％或占降雨量的９５．１％。（２）酸雨通过林冠层后,ｐＨ值明显增加。（３）在马尾松林和常绿阔叶林中,某些单次降雨出现ＳＯ４＾２－、ＮＯ３＾－、ＮＨ４＾＋Ａｌ＾３＋、Ｎａ＾＋的负淋溶现象,说明森林对这些离子（特别是ＮＯ３＾－、Ａａ＾３＋）具有吸收作用;阔叶林全年的ＮＯ３＾－和Ａｌ＾３＋净淋溶为负值,说明阔叶林比马尾松林对这两种离子具有更强的吸收能力。（４）雨水酸度增加（即ｐＨ值减小）,明显提高阳离子Ｃａ＾２＋、Ｍｇ＾２＋、Ｋ＾＋和Ｎａ＾＋冠层淋溶面分率。（５）ＮＨ４＾＋、ＳＯ４＾     

Concentrations of exchangeable bases and cation exchange capacity in soils of cropland, grazing and forest in the Bale Mountains, Ethiopia

Conversion of native forest ecosystem to cropland has considerably degraded the soil nutrient levels in the Bale Mountains, south-eastern highlands of Ethiopia. This study investigated the effects of land use change through conversion of native forest to cropland and/or grazing land on soil pH (H₂O), base cations (Ca²⁺, Mg²⁺, K⁺, Na⁺), CEC and percentage base saturation (PBS) in three adjacent land-use types: cropland, grazing land and native forest. A total of 108 soil samples (3 replications × 3 land-use types × 4 profiles × 3 soil depth layers, 0–0.2, 0.2–0.4 and 0.4–1.0 m) were collected for laboratory analyses. Results showed that soil pH, Na⁺ and K⁺, CEC, and PBS varied significantly with respect to land use and soil depth while Ca²⁺and Mg²⁺ varied with soil depth (ρ < 0.05). Conversion of native forest ecosystem to cropland during a 15-year period significantly increased soil pH and PBS while reducing Na⁺ and K⁺. The CEC in the cropland was reduced by 37.7% (2.6% per annum) compared to the native forest, which could be attributed to the decline in organic matter concentrations. If such rapid declines in soil nutrient concentrations continue unabated, the soils will reach at the point of no return within a few decades. Although the effect of grazing on most of the properties was found to be minimal, adapting the number of stock to the carrying capacity of the land and thereby enhancing the natural regeneration, combined with proper cropland management practices could help restoring soil nutrients for sustainable agricultural production and ecosystem functions.     

Transfer characteristics of nutrient elements through hydrological process of a Pinus tabulaeformis stand in the West Mountain of Beijing

Forest precipitation chemistry is a major issue in forest hydrology and forest ecology. Chemical contents in precipitation change significantly when different kinds of external chemical materials are added, removed, translocated and transformed to or in the forest ecosystem along with precipitation. The chemistry of precipitation was monitored and analyzed in a 31-year-old Pinus tabulaeformis forest in the West Mountain of Beijing. Movement patterns of nutrient elements in hydrological processes can be discovered by studying this monitored data. Also, the information is useful for diagnosing the function of ecosystems and evaluating the impact of the environment on the ecosystem. Samples of rainfall, throughfall and stemflow were collected on the site. In the lab, Ca²⁺ and Mg²⁺ were analyzed by flame atomic absorption and K⁺ and Na⁺ by flame emission. NH₄ ⁺-N was analyzed by indophenol blue colorimetry and NO₃ ⁻-N was analyzed by phenoldisulfonic acid colorimetry. The results showed that: 1) The concentration gradient of nutrient elements clearly changed except for Na⁺. The nutrients in stemflow were significantly higher than those of throughfall and rainfall as the precipitation passed through the P. tabulaeformis forest. The monthly patterns showed distinct differentiation. There are indications that a large amount of nutrients was leached from the canopy, which is a critical function of intra-ecosystem nutrient cycling to improve the efficiency of nutrient use. 2) The concentrations of NO₃ ⁻-N and K⁺ changed more than those of the other nutrient elements. The concentration of NO₃ ⁻-N in throughfall and stemflow was 4.4 times and 9.9 times higher than those in rainfall, respectively. The concentration of K⁺ in throughfall and stemflow was 4.1 times and 8.1 times higher than those in rainfall, respectively. 3) The leaching of nutrient elements from the stand was an important aspect of nutrient return to the P. tabulaeformis forest, which returned a total amount of nutrient of 54.1 kg/hm², with the contribution of Ca²⁺ and K⁺ much greater than that of other elements. Also, K⁺ was the most active element in leaching intensity. 4) Nutrient input through precipitation was the main source in the West Mountain of Beijing and the amount of nutrient added was 66.4 kg/hm², of which Ca²⁺ and N contributed much more than the other nutrient elements. When precipitation passes through the P. tabulaeformis forest, 121 kg/hm² of nutrient is added to the forest floor. Ca²⁺ recorded the greatest nutrient increase, with 61.2 kg/hm², followed by N (NH₄ ⁺-N and NO₃ ⁻-N), K⁺ and Mg²⁺, with 31.3 and 16.5, and 8.11 kg/hm², respectively. The least was Na⁺, 3.34 kg/hm². Translated from Acta Ecologica Sinica, 2006, 26(7): 2,101–2,107 [译自: 生态学报]     

Change in river water chemistry as affected by the confluence of forest drainage water in dairy farming area on Hokkaido Island, Northern Japan

We evaluated i) the difference in river water chemistry between a watershed mainly consisting of pasture and a watershed mainly consisting of forest, and ii) how the chemistry of river draining the pasture is influenced by that of the river draining the forest. We selected one river (designated as the T-river) draining the pasture (3,587 ha), and two rivers draining a forest (738 and 879 ha) in eastern Hokkaido, northern Japan. During higher river flow due to precipitation and thawing, the concentrations of NO ₃ ⁻ , SO ₄ ²⁻ , K⁺, Fe, and Al increased, suggesting the relative importance of the shallow soil layer as their source. On the other hand, Na⁺, Mg²⁺, Ca²⁺, and Si decreased, suggesting the relative importance of the source in a deep soil layer. The concentrations of NO ₃ ⁻ , Cl⁻, SO ₄ ²⁻ , K⁺, Na⁺, Mg²⁺, Ca²⁺, and Fe were higher in the T-river than in the forest drainage waters, suggesting the contribution of the excretion components from the milk cows. The Si concentration exhibited the opposite pattern. The concentrations of NO ₃ ⁻ , Cl⁻, SO ₄ ²⁻ , K⁺, Na⁺, Mg²⁺, Ca²⁺ (p<0.001), and Fe (p<0.05) in the T-river decreased after the confluence of the forest drainage waters, while Si concentration increased (p<0.001). The reason for the change in river chemistry was the confluence of the forest drainage waters. These findings suggested the environmental role of the forest in the dilution of the polluted river. Prof. S. Ohata, and Prof. H. Takeda, Graduate School of Agriculture, Kyoto University, facilitated this study. Prof. T. Sakai, Graduate School of Informatics, Kyoto University, offered this study some convenience. Dr. M. Sakimoto, and Dr. M. Katsuyama, Graduate School of Agriculture, Kyoto University, offered useful advise.     

中亚热带钱江流域天然次生林集水区溪流与降水水质比较

对浙江钱江源生态站大气降水和天然次生林生态系统的径流水质指标进行逐月取样测试和对比分析.结果表明:天然次生林集水区水体中溶解氧含量年平均值达到8.10 mg·L-1,是大气降水的1.12倍;总氮含量年平均值达7.68 mg·L-1,是大气降水的4.49倍.大气降水的生化需氧量年平均值达2.10 mg·L-1,是天然次生...     

Biogeochemical cycling and chemical fluxes in a managed northern forested wetland, Michigan, USA

Forest harvesting and subsequent regeneration treatments may cause changes in soil and solution chemistry that adversely affect forest productivity and environmental quality. The objective of this study was to assess soil carbon (C), nitrogen (N), and base cation pools and fluxes, and to construct a hydrogen ion (H⁺) mass balance to identify major processes controlling acidity production and consumption 14 years following whole-tree harvesting and regeneration in a northern forested wetland with underlying mineral soils derived from calcareous glacial drift. Results for soil elemental and nutrient pools in the harvested/regenerated stand were compared to an adjacent non-harvested stand and a riparian zone. The riparian zone had the highest soil total C, total N, and exchangeable calcium (Ca) and magnesium (Mg) pools; however, no difference in exchangeable potassium (K) was evident among stand types. Moreover, no differences between the harvested/regenerated and uncut stands were evident in any of the soil chemical pools.Net export of base cations was minimal and the H⁺ mass balance indicated that net cation exchange was not a significant process in H⁺ production or consumption in either the uncut or harvested/regenerated stands. The most striking differences in the H⁺ mass balance were (1) eight times the H⁺ consumption from sulfate (SO₄²⁻) reduction in the harvested/regenerated stand compared to that in the uncut condition and (2) nearly twice the H⁺ production due to N immobilization in the harvested/regenerated stand. However, both stand types were net H⁺ sinks and increases in H⁺ export due to whole-tree harvesting were not evident.The riparian zone was a net exporter of base cations. This finding was attributed to a combination of base cation exchange and carbonate mineral weathering; data suggested the importance of the latter. More research, however, is required to isolate the contributions of cation exchange and carbonate weathering on base cation export from the riparian zone. Stream chemistry was consistent with that of the riparian zone, indicating a strong linkage between the riparian zone stream chemistry, and whole-tree harvesting had no intermediate term (i.e., 14 years) effects on stream acidification in this managed northern wetland ecosystem.     

Relationship between streamflow and nutrient and sediment losses from an oak-beech forest watershed during an 18-year long monitoring study in Turkey

The objectives of this study were to quantify the amount of the stream discharge, nutrient fluxes, suspended sediment loss, and to define the relationship between streamflow and these parameters in a forest-covered watershed. The study was carried out in an experimental watershed, which has been monitored since 1979 in the Belgrad forest in Istanbul. Significant linear regressions were obtained between streamflow and discharge of selected water quality parameters. Mean monthly losses were 10.01 kg/ha for HCO₃ ⁻, 5.92 kg/ha for CI⁻, 0.07 kg/ha for total N, 1.29 kg/ha for Mg²⁺, 3.59 kg/ha for Ca²⁺, 2.59 kg/ha for Na⁺, 1.82 kg/ha for K⁺, 0.0113 kg/ha for P-PO₄ ³⁻, and 35.82 kg/ha for suspended sediments. Among the monitored water quality parameters, HCO₃ ⁻, CI⁻, and Ca²⁺ had greater losses than the rest of the chemical parameters studied in the watershed. Net gains (influx exceeded outflux) calculated for total N, Mg²⁺, K⁺, and P-PO₄ ³⁻ in the annual basis can be considered as an addition to the ecosystem’s organic nutrient pool. In contrast, net losses occurred for HCO₃ ⁻, CI⁻, Ca²⁺, and Na⁺.